Colloquia

Summary

Osteochondral lesions of the talus (OLTs) are common ankle injuries. They often occur in young, active patients following traumatic sports injuries. OLTs have a multi-week rehabilitation period that often includes progressive partial weightbearing. The assistive devices currently used during this period lack precise offloading control, limit ankle mobility and can inhibit daily life. This study presents the redesign of a unilateral, adjustable offloading ankle foot orthosis to support this rehabilitation. This design uses a compression spring mechanism which is adjustable by reducing the number of coils used to allow for adjustable offloading between 25% and 50% of bodyweight. Conceptual designs were developed by iterating through sketching, quasi static load cases and Solidworks simulations. The final design has a curved ground contact part which allows the offloading to follow the natural shape of the ankle joint reaction force and minimizes the interference with the normal gait cycle. A first prototype was produced to test this design. A technical validation was conducted using the Zwick Z100 which showed positive results regarding the strength of the prototype and no failures occurred. This allowed a subject test to be performed as a proof of concept whereby one subject was tested using the emed® q pedography platform. During this subject test the offloading reached between 38% and 52% during the first 75% of the stance phase. During the last 25% of the stance phase, the ground contact part did not touch the ground anymore. This proof of concept shows the potential of the offloading with this compression spring-based design for future development.